This disclosure relates to electronic circuits. Some circuits are expected to be operated over a range of operating conditions. For example, circuits that are used in mobile devices may be expected to be operated over a range of supply voltages and temperatures. Changing the operating conditions can change the electrical characteristics of circuit elements in a circuit, which, in turn, can change the behavior of the circuit. It is desirable to design circuits that can continue to operate with sufficiently large margins across the manufactured variation space even when the operating conditions change.